Grinding operations in tube mills using the wet method are generally known in practice. When grinding ore material, an acid treatment operation is additionally necessary, the acid generally being added after the grinding operation and then having to be neutralised after the acid treatment operation. However, this is relatively complex and costly. It would therefore be very desirable for the acid to be able to be recirculated.
Tube mills which are generally used are, however, not designed for a grinding operation with an acid owing to the problem of corrosion of the mill cylinder. Therefore, it has already been considered to produce the mill cylinder from high-grade steel, which would, however, be linked with enormous additional costs.